Volatile isoprenoid

Hick, A. J., Luszniak, M. C. and Pickett, J. A. (1999). Volatile isoprenoids that control insect behaviour and development. Natural Product Reports 16 39-54. 

Volatile isoprenoids that control insect behavior and development have been reviewed.476 Information on the biosynthesis of terpenoids with special emphasis on beetle pheromones has been compiled by Seybold and... 

Several hundred volatile isoprenoid substances that interfere with insect larval moulting have so far been resolved from plants and such phytoecdysones will be dealt with in Chapter 11, which is concerned with development-perturbing compounds binding to cytosolic hormone receptors. It must also be noted that plant cells within a plant (and indeed whole plants themselves) can communicate with each other via volatile signalling bioactives... 

That is to say, the chromoplasts constribution to the volatile isoprenoids of whole daffodil flowers comprises only monoterpene hydrocarbons. 

Vickers CE, Bongers M, Liu Q, Delatte T, Bouwmeester H (2014) Metabolic engineering of volatile isoprenoids in plants and microbes. Plant Cell Environ 37(8) 1753-75. doi 10.1111/ pee. 12316... 

Vickers, C. E., Gershenzon, J., Lerdau, M. T, Loreto, F. (2009) A unified mechanism of action for volatile isoprenoids in plant abiotic stress. Nature Ghent. Biol. 5,283. 

Isoprene metabolism in plants is very complex. Plants can synthesize many types of aromatic substances and volatile oils from isoprenoids. Examples include menthol (1= 2 ), camphor (1 = 2), and citronellal (1 = 2). These Cio compounds are also called monoterpenes. Similarly, compounds consisting of three isoprene units (1 = 3) are termed sesquiterpenes, and the steroids (1 = 6) are called triterpenes. 

A high variety of isoprenoids is also observed for fossil molecules (Fig. 11.1, pink ribbon, first to the left). This suggests that the first cnidarians at Cambrian times have extensively exploited what the terpene chemistry allows (Pietra 1995). Although overshadowed by diagenetic transformations, and not comprising volatiles for obvious reasons, Chart 16.1 is suggestive of the structure of these early isoprenoids. 

To establish unambiguously the length of a hydrocarbon chain or the position of double bonds, mass spectral analysis of lipids or their volatile derivatives is invaluable. The chemical properties of similar lipids (for example, two fatty acids of similar length unsaturated at different positions, or two isoprenoids with different numbers of isoprene units) are very much alike, and their positions of elution from the various chromatographic procedures often do not distinguish between them. When the effluent from a chromatography column is sampled by mass spectrometry, however, the components of a lipid mixture can be simultaneously separated and identified by their unique pattern of fragmentation (Fig. 10-24). 

Insects communicate through the use of a great variety of volatile pheromones. As mentioned in Chapter 8, Section A,l, some moths utilize acetate esters of various isomers of A7 and A11 unsaturated C14 fatty acids as sex pheromones. Some other moths convert the trans-l 1 -tetradecenyl acetate into the corresponding C14 aldehyde or alcohol, while others use similar compounds of shorter (Cn - C12) chain length.143 Some ants use ketones, such as 4-methyl-3-heptanone, as well as various isoprenoid compounds and pyrazines as volatile signaling compounds.144 Other insects also utilize isoprenoids,145 alkaloids,146 and aromatic substances as pheromones. 

The Amazon Indians Waiapi living in the West of Amapa State of Brazil, treat malaria with an inhalation of vapor obtained from leaves of Viola surinamensis. The antimalarial activity of the aromatic volatile plant extracts from leaves, showed that nerolidol (an acyclic oxygenated sesquiterpene) was identified as one of the active principles (36). Another recent study suggested the presence of an active isoprenoid pathway for biosynthesis of isoprenic chains of coenzyme Q in P. falciparum (37), parasites treated with nerolidol showed decreased ability to synthesize coenzyme Q in all intraerythrocytic stages. A challenge would be to now identify which African medicinal plants contain similar chemistry. 

Methylcyclopentanoid monoterpenes are a group of isoprenoids characterised by the presence in their skeleton of a cyclopentanoid residue. Both hydrophilic and hydrophobic compounds are known (refs 1-3 ), which may be both volatile and non volatile. Products of alkaloidal nature (ref 4 ) are also included in this family. 

For moderately weathered oils and refined products (for example, —15 to 30% weathered), significant losses occur in M-aUcanes and relatively low-molecular-weight isoprenoid compounds. Rapid loss of volatile aromatic compounds is clear. When oils are weathered to a certain degree (approximately in the range of 20 to 25% weathering for most oils), the BTEX and C3-benzenes could be completely lost, and the loss of Cq and Cl- naphthalenes can be significant. The ratio of GC-resolved peaks to UCM can be considerably decreased due to the preferential loss of resolved hydrocarbons over the unresolved complex hydrocarbons. The biomarker compounds are enriched. 

PAH compounds are probably the most studied hydrocarbon group in crude oils and refined products. Crude oils and refined products from different sources can have very different PAH distributions. In addition, many PAH compounds are more resistant to weathering than their saturated hydrocarbon counterparts (fx-alkanes and isoprenoids) and volatile alkylbenzene compounds, thus making PAHs one of the most valuable fingerprinting classes of hydrocarbons... 

Hlubucek, J.R., A.J. Aasen, S.O. Almqvist, and C.R. EnzeU Tobacco chemistry. 21. Three new volatile tobacco constituents of probable isoprenoid origin Acta Chem. Scand. B27 (1973) 2232-2234. 

Floral scents are often complex blends of several compounds. These are mainly fatty-acid derivatives, benzenoids, phenylpropanoids, isoprenoids, nitrogen-and sulfur-containing compounds. Knudsen et al. s (1993) comprehensive review of floral odors reported floral scents with as few as three compounds and as many as several hundred. A study of moth-pollinated flowers from the Nyctaginaceae reported as many as 77 compounds in floral scent and as few as one. Studies that have focussed on identifying the site of volatile production in flowers report that they are produced mostly in the petals. Volatiles are both synthesized and released by the epidermal cells or by special glandular trichomes on the petal surface. Other studies have shown that the odor of pollen is also part of the odor signal. ... 

Gas Chromatography. Whereas N.M.R. effectively senses the f mctional groups present in a mixture, differences between retention times enable G.C. to identify individual members (provided they are moderately volatile) of a homologous series such as the n-alkanes. Positive identification requires calibration by co-injection with authentic samples (here n-alkanes) or coupling of M.S. with, preferably, a capillary G.C. column. Although G.C. stick diagrams of n-alkane distributions have been used for comparing extracts from fossil fuels, we advocate acyclic-isoprenoid-hydrocarbon distributions, and particularly the pristane/phytane ratio, as more reliable indicators of fossil fuel maturation 6). 

Monoterpenes are aliphatic or cyclic isoprenoid Cjo-compounds. They usually contain one or two isolated double bonds, but may also be saturated or aromatic. Often hydroxy, keto, aldehyde, carboxylic acid, or ester groups are present (Fig, 99). Most compounds are volatile and lipophilic. 

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